The present invention relates to a system for processing an image which is read on a pixel-by-pixel basis and, more particularly, to an image processing system which transforms a halftone image into a two-level image using dither matrixes.
Dither processing is a method extensively used for processing a halftone image into a two-level image. A problem heretofore encountered with the dither method is that strong moire tends to develop in the resulting image. Moire develops, for example, when a grid pattern, dot photograph or like picture having periodicity is processed. One approach to eliminating moire is varying the threshold matrix in a pseudorandom manner, as disclosed in Japanese Patent Publication No. 55-24634/1980. However, just as it alleviates the moire situation, it brings about another problem that the image quality is lowered when a picture with no peridicity is processed.